Single and double Auger decay of 4f-ionized mercury including cascade and direct processes

Single (SA) and double (DA) Auger decay including cascade and direct processes are investigated for Hg 4f^-1 with multiconfiguration Dirac-Fock method and two-step approaches, i.e., knockout and shakeoff mechanisms. Due to the computational effort, only the major transitions are considered to describe the SA and DA decays for the Hg⁺ ions with complex electronic configurations. In order to estimate the Auger transition energies and amplitudes, the reference configuration sets producing the configuration state functions are carefully chosen for balancing electron correlations among the successive singly, doubly and triply ionized mercury. The Auger rates and electron spectra, DA probabilities as well as the populations of the final Hg³⁺ states are obtained. Our results well explain the recent experimental data about the 4f hole states of HgPalaudoux J et al., Phys. Rev. A 91 012513 (2015), and could provide guidance for further studies on complex atoms. Particularly for the DA decay, the contributions of the direct processes, which are neglected in their calculations, are found to be important, accounting for as high as about 38% and 34% of the total DA decays for the 4f_7/2^-1 and 4f_5/2^-1, respectively.